"packet size per a tick" and "8192EU/t per Tick".
It might be lines like those that don't help in the confusion between "per packet' (/p) and "per tick" (/t).
A packet is how much energy is generated or output by a single machine.
8192/p means that it would not accept the power coming from a machine that output more than that at once. On the top of my head, I can't remember of a single contraption that can output as much in a single block anyway. Even lightning rods only output packets of 8192 EU.
A tick is the smallest unit of time that the game is using for its calculations. In a perfect environment, 20 ticks = 1 second.
Most machines can only accept or output a set amount of energy every tick, like your ultimate solar panel outputting 512EU/t.
Where it gets complicated and messes up people's mind is thatthe very same solar panel will output his energy in a single packet into your EU network. That packet will have a size of 512 EU.
As I am writing it, I see that my explanation is not really making things clearer for me, so let's just sum it up by saying that if you are not playing ultimate version 1.0.2, then all your solar will actively speed up the fabricator. If you are on that version, putting more than 16 will make it originally charge its buffer faster, ut not operate faster.
That being said, as solar doesn't work as well during the night, it might be good to have 1 or 2 extras to charge a bit more for the night.